Optical methods for estimating apparent density of sediment in suspension

Alexander J. Hurley , Paul S. Hill , Timothy G. Milligan , Brent A. Law
{"title":"Optical methods for estimating apparent density of sediment in suspension","authors":"Alexander J. Hurley ,&nbsp;Paul S. Hill ,&nbsp;Timothy G. Milligan ,&nbsp;Brent A. Law","doi":"10.1016/j.mio.2016.09.001","DOIUrl":null,"url":null,"abstract":"<div><p><span><span>In most aquatic environments, suspended sediment is composed of loosely packed particle aggregates, termed flocs that have variable apparent densities. The apparent density of flocs, which is defined as particle dry mass over wet volume, is an important variable because it affects </span>settling velocity and vertical sediment flux. Two established methods exist for measuring apparent density. One method uses physical measurements of sediment mass concentration combined with measurements of particle volume concentration from </span>optical instruments to estimate apparent density. This method is laborious because it requires the collection of water samples, so it is not conducive to construction of high-resolution time series of density. Another method uses video observations of particles in a settling column to measure particle size and settling velocity. These measurements are used to solve for apparent density according to Stokes Law. The goal of this study is to develop a new method that uses the ratio of particulate beam attenuation to particle volume to estimate apparent density of sediment in suspension. Data from five studies are used to compare density estimates with the new method to the previous methods. The new optical method produces apparent densities that are correlated linearly with measurements of the ratio of dry mass to wet volume. However, the new optical method produces density estimates that do not correlate with video estimates of apparent density. This lack of correlation is due to sampling bias of the video method, which has a relatively large lower limit of resolution in particle size. Development of a higher resolution camera would eliminate the current bias in particle size and would enable further assessment of the new optical method as an accurate proxy for apparent density.</p></div>","PeriodicalId":100922,"journal":{"name":"Methods in Oceanography","volume":"17 ","pages":"Pages 153-168"},"PeriodicalIF":0.0000,"publicationDate":"2016-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.mio.2016.09.001","citationCount":"12","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Methods in Oceanography","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S2211122016300226","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 12

Abstract

In most aquatic environments, suspended sediment is composed of loosely packed particle aggregates, termed flocs that have variable apparent densities. The apparent density of flocs, which is defined as particle dry mass over wet volume, is an important variable because it affects settling velocity and vertical sediment flux. Two established methods exist for measuring apparent density. One method uses physical measurements of sediment mass concentration combined with measurements of particle volume concentration from optical instruments to estimate apparent density. This method is laborious because it requires the collection of water samples, so it is not conducive to construction of high-resolution time series of density. Another method uses video observations of particles in a settling column to measure particle size and settling velocity. These measurements are used to solve for apparent density according to Stokes Law. The goal of this study is to develop a new method that uses the ratio of particulate beam attenuation to particle volume to estimate apparent density of sediment in suspension. Data from five studies are used to compare density estimates with the new method to the previous methods. The new optical method produces apparent densities that are correlated linearly with measurements of the ratio of dry mass to wet volume. However, the new optical method produces density estimates that do not correlate with video estimates of apparent density. This lack of correlation is due to sampling bias of the video method, which has a relatively large lower limit of resolution in particle size. Development of a higher resolution camera would eliminate the current bias in particle size and would enable further assessment of the new optical method as an accurate proxy for apparent density.

估计悬浮液中沉积物表观密度的光学方法
在大多数水生环境中,悬浮沉积物由松散堆积的颗粒聚集体组成,称为絮凝体,具有可变的表观密度。絮凝体的表观密度,定义为颗粒干质量比湿体积,是一个重要的变量,因为它影响沉降速度和垂直泥沙通量。现有两种测定表观密度的方法。一种方法是利用沉淀物质量浓度的物理测量与光学仪器测量的颗粒体积浓度相结合来估计表观密度。该方法由于需要采集水样,所以比较费力,不利于构建高分辨率的密度时间序列。另一种方法是通过视频观察沉降柱中的颗粒来测量颗粒大小和沉降速度。根据斯托克斯定律,这些测量值用于求解表观密度。本研究的目的是建立一种利用颗粒束衰减与颗粒体积之比来估计悬浮沉积物表观密度的新方法。来自五项研究的数据被用来比较新方法和以前方法的密度估计。新的光学方法产生的表观密度与干质量与湿体积之比的测量呈线性相关。然而,新的光学方法产生的密度估计与视频估计的表观密度不相关。这种相关性的缺乏是由于视频方法的采样偏差造成的,视频方法在粒度上的分辨率下限相对较大。更高分辨率相机的开发将消除目前颗粒尺寸的偏差,并将使进一步评估新的光学方法作为表观密度的准确代理。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 求助全文
来源期刊
自引率
0.00%
发文量
0
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术官方微信